1. Field of the Invention
This invention relates to the reduction of weight in automotive vehicles, and, more particularly, to a door assembly utilizing magnesium to reduce weight and increase fuel economy.
2. Background of the Invention
During the last decade, manufacturers of automobiles have undertaken steps to reduce weight of the vehicles in order to improve fuel economy and to reduce vehicle emissions. Such efforts have included the design of automotive vehicle components utilizing light metal alloys, leading to a variety of applications in chassis and power train components. More recently, advances in high-pressure die-casting technologies have enabled these technologies to be applied to larger structural components. Noteworthy examples of such larger components are instrument panel reinforcements, seat frames and door closure panels. While weight reductions of 40% can be realized through the use of magnesium, product engineers are faced with new challenges to incorporate adequate stiffness and crash critical applications with a material system possessing lower modulus and ductility compared to conventional formed sheet metal construction of such components.
Increasing the numbers of materials to be utilized in the construction of large structural components for automotive vehicles requires alternative joining strategies for the disparate materials in the assembly of such structural components. Consideration must be given to galvanic corrosion, as well as to differences in thermal expansion rates. Other related issues include the integration of the new materials and assembly techniques into the existing framework of an automotive manufacturing and assembly plant.
In U.S. Pat. No. 5,536,060, issued to Moinuddin Rashid, et al. on Jul. 16, 1996, an automotive door assembly is disclosed in which a reinforcement panel is attached to the interior side of the outer panel of the door assembly. This reinforcement panel is described as having superplastic forming qualities such as aluminum and stainless steel, but acknowledges that magnesium can be employed optionally, to provide the complex shape required in the specific reinforcement panel designed for the disclosed application.
In U.S. Pat. No. 4,662,115, issued to Takegi Ohya, et al. on May 5, 1987, an automotive vehicle door assembly is disclosed incorporating the employment of an inner panel formed of steel and an outer panel formed of synthetic resin. The hinge and door closure and locking devices are mounted on the steel inner panel.
U.S. Pat. No. 5,924,760, was issued to Paul Krajewski, et al. for a one piece corrugated anti-intrusion barrier for an automotive vehicle door. This anti-intrusion barrier is preferably formed in a corrugated configuration from a piece of sheet metal stamped into the preferred form. These barrier panels are preferably formed from aluminum alloys, though other materials including magnesium, steel, and titanium can be alternatively utilized.
U.S. Pat. No. 5,944,373, issued to Dinesh Seksaria on Aug. 31, 1999, is directed to a lightweight tailgate assembly for a pick-up truck in which a plastic reinforcing member is positioned between two metal panels to form the completed tailgate assembly. The inner and outer tailgate panels may be formed of aluminum or magnesium to minimize weight considerations.
In U.S. Pat. No. 6,068,327, issued to Michael Junginger on May 30, 2000, an upwardly folding rear cargo door for an automotive vehicle is disclosed. Junginger indicates that magnesium would be material preferred over aluminum, steel and plastic because of the reduction in weight of the assembly without the loss of strength. Junginger, however, does not disclose how a composite door structure incorporating magnesium with other structural materials can be effectively combined to create a vehicle door assembly.
U.S. Pat. No. 4,919,473, issued to Johann Laimighofer on Apr. 24, 1990, is directed to a structural beam for incorporation into an automotive vehicle door as an anti-intrusion device. Like the other references noted above, Laimighofer acknowledges that the structural beam may be formed from magnesium, but does not address the issues of how the disparate materials may be properly joined and deployed into a composite vehicle door assembly.
It would, therefore, be desirable to provide a composite automotive vehicle door assembly formed from disparate materials to provide a lightweight door assembly without sacrificing strength and intrusion resistance.
It is an object of this invention to overcome the aforementioned disadvantages of the known prior art by providing a composite vehicle door assembly utilizing disparate structural materials to form the components thereof.
It is another object of this invention to reduce the weight of a vehicle door assembly, when compared to conventional vehicular door assemblies, by using lightweight structural materials.
It is an advantage of this invention that fuel economy for automotive vehicles is increased while vehicle emissions are reduced.
It is a feature of this invention that improved joining strategies are provided to permit the effective mounting and connection of disparate structural component materials.
It is still another object of this invention to provide a composite vehicle door assembly that utilizes an outer door panel formed of aluminum, an inner door panel formed of magnesium, a mounted intrusion beam formed of composite materials, and an internal hardware module formed of thermoplastic.
It is another feature of this invention that the inner door panel can be manufactured from magnesium using high-pressure die-casting techniques.
It is still another feature of this invention that the assembly of the vehicle door components and the mounting of hardware and other components to the magnesium inner door panel is accomplished through the use of two-part inserts.
It is another advantage of this invention that the two-piece thermoplastic fastener inserts provides a dielectric barrier between the fastener and the magnesium inner door panel to prevent corrosion at the interface therebetween.
It is still another advantage of this invention that the fastener holes in the magnesium inner door panel can be formed by machining, piercing, or by casting in place followed by a clean-out during trimming.
It is yet another feature of this invention that the assembly of the aluminum outer door panel and the magnesium inner door panel can be accomplished through a hemming process.
It is yet another advantage of this invention that an increased flange hem thickness on the magnesium inner door panel casting provides an acceptable radius of curvature for the aluminum outer door panel to permit the utilization of a hemming process for assembly of the inner and outer door panel components.
It is yet another object of this invention to provide an affordable corrosion protection solution for use in a mixed material vehicular door assembly system that offers a satisfactory performance in the aggressive environment of a vehicle door closure.
It is a further feature of this invention that the magnesium inner door casting can be formed with a seal channel that encapsulates the seal mounted on the body of the vehicle.
It is a further advantage of this invention that the capture of the door seal within a formed seal channel improves noise reduction and performance of the seal.
It is a further feature of this invention to incorporate the hinges for the vehicle door assembly on the magnesium inner door panel.
It is a further object of this invention to provide a composite reinforcement beam to provide an anti-intrusion device for the vehicular door assembly.
It is still a further feature of this invention that the reinforcement member can be formed from an outer layer of a polymer composite material reinforced with glass or carbon fibers with an interior core of polyurethane.
It is yet another feature of this invention that the shaped interface between the composite reinforcing beam and the corresponding mounting lugs formed in the inner door panel increase improves the load transfer from the reinforcing beam to the inner door panel during impacts.
It is still a further advantage of this invention that the composite reinforcement beam has a reduced weight compared to conventional steel reinforcement beams.
It is yet a further feature of this invention that the vehicle door assembly incorporates a modular concept to decrease complexity of assembly.
It is still a further object of this invention to provide a door hardware module on which substantially all of the hardware required for the vehicle door can be mounted.
It is still another feature of this invention that the door hardware can be pre-assembled on a module component for installation on the inner door panel as a unit.
It is yet a further advantage of this invention that the assembly of a vehicle door is made less complex by reducing the number of assembly operations and by using a modular configuration.
It is still another feature of this invention that the inner door panel can be formed with integrated reinforcements cast into the panel to increase resistance to impacts without adding reinforcement attachments to the door structure.
It is a further object of this invention to provide a lightweight vehicle door assembly that is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use.
These and other objects, features and advantages are accomplished according to the instant invention by providing an anti-intrusion beam for incorporation into a vehicle door assembly. The outer skin is formed from laminated layers of composite materials having fiber reinforcement oriented in a directional pattern in each respective layer. The anisotropic beam includes body members having an interior core formed of high density foam plastic. The transversely corrugated beam includes attachment areas that have the same corrugated configuration which are fastened to mounting lugs of an inner door panel arranged in a corresponding corrugation. Variations in the thickness and formation of the layers of the outer skin can be used to control the failure of the beam during impact to provide a progressive predicable failure pattern for the beam. A frame catcher can be inserted into the body portions of the anti-intrusion beam to permit the transfer of impact forces to the frame of the vehicle.